Prior art potentiometers are known wherein a variable center contact is moved across or along a resistive element. The resistive element can be a continuously extending region of resistive material. Alternately, it can be formed of a plurality of overlapping or abutting resistive materials of different lengths or resistivities.
Such potentiometers are known to suffer from noise problems since the conductive wiper blade moves on the resistive material directly. An alternate prior art potentiometer structure utilizes a plurality of spaced-apart conductive members with resistors coupled therebetween. The wiper element moves along the conductive regions and not on the resistors themselves. This structure requires the ability to precisely deposit a plurality of spaced-apart conductive regions as well as the ability to precisely deposit a plurality of spaced-apart resistors linking spaced-apart conductive regions.
As potentiometer sizes get smaller and smaller, it becomes more difficult and expensive to precisely define the shape and structure of the spaced-apart conductive pads, as well as the resistor elements linking same.
Another disadvantage of prior art potentiometers formed with spaced-apart conductive regions is that as the wiper blade moves from region to region conductive material migrates into the space between the conductive shapes. Eventually enough of this conductive material is spread between the two-spaced apart pads to short out the resistor therebetween.
Another disadvantage of prior art potentiometers which incorporate spaced-apart conductive regions arises because it may be desirable to laser trim the resistor element between pairs of conductive elements to enhance the precision of the resultant potentiometer. Such trimming requires smaller and smaller probes capable of electrically contacting the two spaced apart conductive pads adjacent to one another. As it becomes more and more important to create smaller and smaller potentiometers, the probes required for trimming a resistive element between spaced apart conductive pads become smaller and smaller and more expensive.
Thus, it would be desirable to be able to form variable resistance or potentiometer elements which exhibit low noise with precisely defined resistance values varying over five or six or more orders of magnitude, in an economical fashion. Preferably, precision resistance values can be achieved without any need for precisely controlling the dimensions or shapes of resistance value. Further, it would be desirable to be able to achieve this result using two non-moving probes during the process of adjusting resistance values.